This invention relates to starting motors for automotive engines, and more particularly to a drainage structure of the front bracket forming part of the housing structure thereof.
Let us first describe the drainage structure of the front bracket forming part of the housing of a conventional engine starter, wherein reference is made to FIG. 1, which shows an axial section of the essential portion of an engine starter.
The starter shown in FIG. 1 comprises a motor portion 1 accomodating an electric motor, whose armature shaft (i.e., rotor shaft) 2 is coupled, via a planetary reduction gear 3, to an overrunning clutch (i.e., one-way clutch transmitting torque only in one rotational direction) 4. A pinion 5 formed integrally with the clutch inner member of the overrunning clutch 4 is axially slidably supported on the output shaft 6 together with the overrunning clutch 4; the pinion assembly including the pinion 5 and the clutch 4 are translated on the output shaft 6 in the axial direction thereof by means of a lever 7 rotatably supported on a fulcrum portion 7a of the lever. One end of the lever 7 (shown at the top in FIG. 1) is engaged with a plunger 8a of an electromagnetic switch 8, while the other end thereof (shown at the bottom in FIG. 1) is engaged with a rear portion of the overrunning clutch 4.
Further, a front bracket 9 forming part of the starter housing is attached to the front end side of the motor portion 1, so as to support the electromagnetic switch 8, the lever 7, the output shaft 6, etc. (It is to be noted that the electromagnetic switch 8 is disposed, as described in detail below, substantially horizontally alongside of the motor portion 1 with a slight, downward inclination with respect to a horizontal plane including the motor axis as shown clearly in FIG. 2, which shows the rear end view of the front bracket.) The front bracket 9 comprises, in addition to the portion accomodating the clutch 4, the pinion 5, the output shaft 6, etc., two further portions: a switch box portion 10 (shown at the top in FIG. 1 and at the left in FIG. 2) in which the front end portion of the plunger 8a of the electromagnetic switch 8 and one arm of the lever 7 is accomodated; and a lever box portion 11 (see FIG. 2) supporting and accomodating the fulcrum portion 7a of the lever 7. As shown in FIG. 2, a tortuous drainage port 12 is formed at the bottom of the switch box portion 10 to communicate the interior of the switch box portion 10 to the outside. Incidentally, reference numeral 13 (at the lower right side in FIGS. 1 and 2) designates an opening at which the ring gear of the internal combustion engine is positioned so as to be engageable with the pinion 5 when the starter is attached to the engine; further, reference numeral 14 designates a stopper for limiting the forward translation of the pinion 5, and reference numeral 15 designates a bearing fitted to an opening formed in the front end of the front bracket 9 to support the front end of the output shaft 6.
The general method of operation of the starter of FIGS. 1 and 2 is well known: The electromagnetic switch 8 is energized when a key switch (not shown) of the automobile is turned on, so that by means of the resulting attraction of the plunger 8a (toward the left in FIG. 1), the lever 7 is turned counterclockwise as viewed in FIG. 1, to translate in the forward direction (toward right in FIG. 1) the pinion assembly including the overrunning clutch 4 and the pinion 5. As a result, the pinion 5 is engaged with a ring gear (not shown) of the engine situated at the opening 13. At the same time, a torque is generated by the motor portion 1 so as to rotate and drive the pinion 5 and thereby start the engine.
In an environment where the automobile runs through puddles, etc., water may intrude into the interior of the starter due to the suction of water through the junction between the front bracket 9 and the electromagnetic switch 8, etc., or due to the splashing up of water at the side of the engine, which splashing up of water results in an intrusion of water into the starter from the opening 13 of the front bracket 9, etc. In the case where the electromagnetic switch 8 is situated substantially horizontally alongside the motor with a slight downward inclination as shown in FIG. 2, the water entering into the switch box portion 10 of the front bracket 9 is drained through the drainage port 12 as indicated by the arrows in FIG. 2.
The above drainage structure, however, suffers from the following disadvantage. Namely, in the case where the starter is in a severe water flooding environment--especially in the case where a lot of water splashed up at the side of the engine intrudes into the starter via the opening 13 in the front bracket 9--the water which, after intruding into the front bracket 9 via the opening 13, etc., enters into the switch box portion 10 via the lever box portion 11 thereof, enters, if the amount of intruding water exceeds the drainage capacity of the drainage port 12, into the interior of the electromagnetic switch 8, the switching function of which switch is then adversely affected by the intruding water.